A multiplicity of actuators have been described in the prior art in the read/write heads of optical storage recorder/player units which control both the focusing and the tracking of the laser beam on optically distinct regions. Typically, the objective lens of the actuator is moved by linear moving coil motors and is suspended in such a fashion that the lens can be displaced along two orthogonal axes. One of the orthogonal axes is the vertical axis (i.e., an axis perpendicular to the storage surface) which is used for focusing. The second orthogonal axis is horizontal and is used for positioning the laser beam relative to signal tracks on the storage surface. By way of specific implementation of the suspension of the objective lens in an optical read/write system, the actuator described in the U.S. Pat. No. 5,199,014 incorporates two injection molded plastic structures attached at opposite sides of the lens housing. Other suspension systems found in the related art use wires, i.e., U.S. Pat. No. 4,782,475, rubber structures, or metal blades, i.e., U.S. Pat. No. 5,136,558, etc. In all the foregoing implementations, suspension design requires dynamic performance without resonances in the desired range of operating frequencies (excluding the first natural frequency). The motors of the actuator must provide a predetermined amount of driving force to accelerate the lens and the associated housing. The actuator package should be easily assembled and should be compact enough to fit in the limited volume available in the contemporary optical disc drive mechanisms. The actuator should be capable of being fabricated at low cost despite the fact that most actuators described in the related art are complicated and consist of many different parts requiring a high degree of accuracy combined with an elaborate and time consuming assembly.
A need has been felt for a two-axis actuator characterized by a high degree of simplicity, a low number of parts, relaxed requirements with respect to accuracy, and, as a result, a low cost in manufacturing and assembly of the actuator.